Different seals are known for sealing shaft passages. Radial shaft sealing rings, slide ring seals, and the like are widely used and their use areas are considerable. A common aspect of all seals, however, is that they are subject to wear and once they have lost their sealing function, they must be replaced. In such cases, leaks that develop must be prevented because, in many applications, they can cause major damage. Hence, the need exists for timely detection of an undesirable leak of a liquid or a gas so that the defective seal may be replaced.
A system for detecting a leak at a seal is known from DE 100 61 111 A1. The leak detection system of DE 100 61 111 A1 includes a depot for storing the leaked material and a sensor based on an optical principle. The sensor transmits a signal when the optical properties of the depot change as a result of the depot being covered by the leaked liquid.